It is important that we keep food cold. When food is cold it will not spoil or go bad. However, if we keep things frozen for too long it can cause freezer bite or other damage. This is why it is important to keep up with commercial refrigeration for our food.
The basic principles of the thermodynamic cycle
The key to understanding refrigeration is to understand the thermodynamic cycle. This cycle is most commonly used in commercial refrigeration systems because it is effective at reducing temperatures. The idea is that we have a gas that will absorb heat from whatever it surrounds and then pass this on to other parts of the system as it changes to a liquid and then a solid.
When we look at this cycle, we can see that there are four main parts:
The compressor The condenser Evaporator Expansion valve
These four things form the thermodynamic cycle and they all play an important role in getting us our desired temperature. They are efficient, but they can only reduce temperatures at a certain rate.
We have different types of refrigeration systems that use the thermodynamic cycle to get us our desired temperature. These are referred to as vapor compression refrigeration and we will look at these in more detail.
The vapor compression system of commercial refrigeration
Using the same thermodynamic cycle as the commercial refrigerator, we use two fridges to split up the work. One fridge is used in each of the four stages. The first fridge is called a condensing unit and this one takes care of reducing temperatures for us by using compression.
The second fridge is called an evaporator/compressor system and this one uses a mixture of pressure and evaporation to reduce temperatures. This is the important part as it gets us close to our desired temperature, but it cannot get below freezing because it takes time for heat to transfer from liquid water into frozen water.
The condensing unit is left at around 15 degrees Celsius while the evaporator gets down to around minus twenty degrees. This allows us to get as cold as we want, but only to the point that water will freeze.
So, the next time you look at a frozen piece of meat or other frozen food product, really understand the process it goes through from its creation to your plate.